This invention relates to an oscillator, comprising a capacitance, charging means and discharging means for charging and discharging the capacitance, respectively, feedback means for activating the charging means and discharging means in dependence on an oscillator signal, and an amplifier for amplifying the capacitance voltage.
An oscillator of this kind is generally known, for example, as a multivibrator in the form of two cross-coupled inverter circuits, the capacitance being coupled between non-inverting outputs thereof. In order to generate two squarewave signals exhibiting a phase shift of 90.degree., a differential amplifier is connected across the capacitance. A first squarewave signal is available between inverting outputs of the inverter circuits, and a second squarewave signal is available on complementary outputs of the differential amplifier. A drawback of the known oscillator is that between the two squarewave signals a phase difference occurs which depends, for example, on the spread in technology-dependent parameters and on frequency-selective parasitic effects. These parasitic effects are more prominent as the oscillation frequency is higher.
It is a further drawback of the known oscillator that the phase difference is not controllable, for example in order to compensate for said disturbing effects.